1. Field of the Invention
This invention is directed to control and monitoring systems and, more particularly, to control and monitoring of loads powered by a panelboard.
2. Background Information
An electrical distribution system within an industrial, commercial or residential property starts at the utility service entrance and ends at the final utilization equipment or loads. The service entrance includes the utility company's wattmeter or kWh meter. Beyond the utility company's meter is a main circuit interrupting device, such as a circuit breaker. The main circuit breaker supplies power to a number of feeder circuits which in turn power a number of branch circuits. In a small system, such as a home, the main circuits directly feed individual branch circuits and no feeder circuits are employed. The electrical utilization loads are normally located on the branch circuits.
An energy management system (EMS) employs on-line or dynamic measurement of the energy consumed by the various electrical loads within the electrical distribution system. With these energy measurements, the EMS may log energy consumption on a per load basis and make load shed or restore decisions based on this information and the desired system strategy. Typically, such strategies involve cost avoidance by energy demand limiting or energy consumption time shifting based on time-of-day energy billing rate structures. Loads which are typically monitored and controlled include water heaters, pool pumps, air conditioners and other cyclic loads which may be time shifted without significantly affecting the energy consumer's comfort level.
The utility's meter forms the "point of common coupling" between the energy supplier (e.g., the utility company) and the energy consumer. Both the energy supplier and the energy consumer have an interest in an efficient energy management system. The utility company has an interest in peak demand limiting or load leveling. The energy consumers are interested in minimizing their energy bill and in having the ability to restore loads shed by the utility company should they choose. Both the utility company and the energy consumers are interested in determining the energy consumption per branch circuit.
Electrical switching devices include, for example, circuit switching devices and circuit interrupters, such as circuit breakers, contactors, motor starters, motor controllers and other load controllers. Circuit breakers are generally old and well known in the art. Examples of circuit breakers are disclosed in U.S. Pat. Nos. 4,553,115; 4,642,726; 4,654,614; 4,887,057; 5,200,724; and 5,341,191. Such circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high level short circuit condition.
Some circuit breakers employ a solenoid having a plunger for engaging a trip mechanism along with a remotely controllable coil for energizing the solenoid. Some circuit breakers employ a status contact for reporting the status of the circuit breaker's separable contacts.
A panelboard holds a plurality of electrical switching devices each of which is connected between one or more power sources and a separate load. An example of an external computer for a panelboard is disclosed in U.S. Pat. No. 4,918,566. It is also known to employ a computer within a panelboard.
It is known to employ electronic control, such as a computer, for controlling the solenoids of a plurality of circuit breakers in a panelboard. It is also known to employ the computer to monitor the status of the circuit breakers in a panelboard from the status contacts.
It is known in EMS systems to provide intelligent demand side management or prediction of which devices are energized and the statistical inhibition of selected devices, although such systems are believed to be either too inaccurate or too expensive to be practical in a commercial or residential EMS system.
There is a need, therefore, for an improved apparatus to monitor branch circuit power or energy consumption and provide on/off control of the branch circuit.
There is a further need for such an apparatus which provides control and monitoring remote from the electrical switching device of the branch circuit.